Creating Excel Spreadsheets with Office Web Components (OWC), Part 3

In Part 2 we looked at the private member variables of
our class as well as our Class_Initialize() and Class_Terminate()
event handlers and our Property Let statements. In this final part we'll examine
the two methods of the ExcelGen class and look at how to use this class through
an ASP page!

Creating the Methods for the ExcelGen Class
Only two methods are needed for our class. The first one, GenerateWorksheet,
accepts a single parameter: a populated Recordset object. This method then loops through
the Recordset, transferring its contents to objSpreadsheet's Cells.
Note that both the data from the Recordset and the names of the columns in the Recordset
are outputted to the Excel spreadsheet.

Class ExcelGen
...
Sub GenerateWorksheet(objRS)
'Populates the Excel worksheet based on a Recordset's
'contents. Check to make sure we have data to show
If objRS.EOF then Exit Sub
Dim objField, iCol, iRow
'Set the iCol/iRow vars to the proper offsets
iCol = iColOffset
iRow = iRowOffset
'Display the names of the columns in the Recordset
For Each objField in objRS.Fields
objSpreadsheet.Cells(iRow, iCol).Value = objField.Name
iCol = iCol + 1
Next 'objField
'Display all of the data
Do While Not objRS.EOF
iRow = iRow + 1
iCol = iColOffset
For Each objField in objRS.Fields
'If the column contains a null value, insert blank string
If IsNull(objField.Value) then
objSpreadsheet.Cells(iRow, iCol).Value = ""
Else
objSpreadsheet.Cells(iRow, iCol).Value = objField.Value
End If
iCol = iCol + 1
Next 'objField
objRS.MoveNext
Loop
End Sub
...
End Class

Our last method, SaveWorksheet, accepts a single parameter, strFileName,
which specifies the location to save the spreadsheet. This method returns a Boolean value:
True if the file is saved successfully, False otherwise. Recall that exporting the Spreadsheet
object to a physical Excel file can fail if the IUSR_machinename account
has inadequate permissions.

Using the ExcelGen Class from an ASP Page
Now that we've looked at the contents of our class, let's examine how to use it through an
ASP page to create a spreadsheet containing the contents of a Recordset! It is highly recommended
that you place the ExcelGen class in an include file and then use a server-side
include on those ASP pages that need to utilize the class's functionality. (To learn more about
server-side includes be sure to read: The Low-Down on #include.)
For this example we'll assume that the ExcelGen class has been placed in the file
/scripts/ExcelGen.class.asp.

To use this class, then, we'll use a server-side include to import the contents of
/scripts/ExcelGen.class.asp. Next, we'll create an instance of the class using
the New keyword. Once we've created and populated a Recordset, we can call the
.SaveWorksheet method to dump the Recordset's contents into an Excel spreadsheet.
Finally, we need to save the contents of the spreadsheet using the .SaveWorksheet
method.

If the spreadsheet is saved successfully the user is presented with a hyperlink to
download the Excel file.

Conclusion / Caveats
One annoying thing with the ExcelGen class is that a user must go through a
two-phase step to view the contents of a Recordset through an Excel file. First, he must
visit an ASP page that creates the Recordset; next, he must click on the link to the
Excel file. This is a pain and something I plan on fixing in the next article on this topic
(which will serve, basically, as an enhancement to the ExcelGen class).

One major concern that should also be quickly apparent is that in the above example the
Excel spreadsheet is always saved to the same file. Urg. This is bad since multiple users
will be trying to access the same file and, most likely, they would be running different
kinds of database queries producing varrying output. One approach is to create a unique
file for every user visiting the page... but then how to we clean up old spreadsheets?
We'll examine this topic in more detail in a future article...

In the mean time, play with the code here, create your own spreadsheets, and poke around the
Microsoft documentation.
Happy Programming!